Carbon build up on 2024 cars with check engine

[mike1957]

so 2024 imprezza low mileage, check engine light
2024 crosstrek check engine light
both cars annoying check engine, no solution our mechanic dealer suggested gas cap
finally brought it in, the cross trek my daughers car,
dealer said a carbon buildup its a problem there finding more and more less than 12 thousand miles.
next week they need it for two days, to go through engine remove the carbon and to go through the engine to find out what is going on, they don't have a clue. no charge its all under warranty barely 10 thousand miles on my car. i think around 12 thousand on daughters,
dealer was good, its warranty work no charge but still need cars for two days.
annoying two brand new cars, and im driving a 2013 dodge caravan that i never did anything but change the oil.
thoughts or any insights anyone,
like i said dealer and subaru canada has no clue

 

[Dick Foster]

Something isn't quite right. What are you using for fuel? Where are you located? At what altitude?

 

[mike1957]

regular gas, and calgary at 3400 ft,
dealer has car tomorrow for two days we shall see what they say, i guess there doing an engine tear down to see what is going on. my car is next, they don't have a clue for so low milage it shouldn't happen but i understand were not the only ones.

 

[izzyman]

This is all due to the start stop function and the cars being tuned for fuel efficiency instead of performance.

I used to rebuild motorcycle engines as a hobby and observed many conditions over time. I found people who rode their motorcycles very leisurely would have far more issues with carbon buildup and fuel system gunk. In some cases I would just do an Italian tune-up and be done with it.

I've had three Subarus with these functions, all post 2020 and I've noticed when they are operating in "I" mode that engine temps rarely get over 200. You need to get the oil temperature over about 212 have to boil off the accumulated moisture in the oil and cook any residual carbon in the combustion Chambers. This is the essence of an Italian tune-up.

Secondly, the start-stop mechanism prevents the engine from warming up sufficiently. Also, when the engine is not turning oil can pool in galleys of the crankcases and the dirt and accumulated carbon sits and is cooled and reheated constantly. It doesn't take much temperature variation to cause this.

All internal combustion engines need to be brought up to temperature for a sustain period now and then. At least once a week you should take your car on the highway turn off the efficiency modes and get the oil temperature over boiling point of water

 

[SJUMBA93]

regular gas, and calgary at 3400 ft,
dealer has car tomorrow for two days we shall see what they say, i guess there doing an engine tear down to see what is going on. my car is next, they don't have a clue for so low milage it shouldn't happen but i understand were not the only ones.

Are you using the Canadian equivalent of a "Top Tier" gas? Also, I periodically give all three of my vehicles a dose of Techron complete fuel system cleaner.

 

[Daniel Renaud]

so 2024 imprezza low mileage, check engine light
2024 crosstrek check engine light
both cars annoying check engine, no solution our mechanic dealer suggested gas cap
finally brought it in, the cross trek my daughers car,
dealer said a carbon buildup its a problem there finding more and more less than 12 thousand miles.
next week they need it for two days, to go through engine remove the carbon and to go through the engine to find out what is going on, they don't have a clue. no charge its all under warranty barely 10 thousand miles on my car. i think around 12 thousand on daughters,
dealer was good, its warranty work no charge but still need cars for two days.
annoying two brand new cars, and im driving a 2013 dodge caravan that i never did anything but change the oil.
thoughts or any insights anyone,
like i said dealer and subaru canada has no clue

Do you use LIQUI MOLY Jectron fuel Injection Cleaner that remove carbon from the injectors?

 

[mike1957]

interesting comments. thankyou for your replies
i have to admit i hate the stop start function. usually turn it off, in canada, the winters are cold and no the engine never really warms up, the temp is actually quite a bit less then 212
and yes will invest in fuel system cleaner, when we get it back from dealer.
and will get back to you with what the dealer finally has to say.
its werid though, both cars low milage, my daughter drives much harder then me, with 11 or 12 thousand miles the engine should be clean.
we buy gas from costco regular, i believe it is top tier
the dealer has it for two days engine tear down to see what is going on, will tell you what they say

 

[izzyman]

If your 2024 model has the smaller infotainment screen and not the huge IMAX garbage, then you can buy a start stop defeat circuit that installs behind the disable button. I got mine off Amazon for $30. It took me literally 5 minutes to install and changes the function so the feature is disabled by default

 

[mike1957]

so dealer finally got the car back, lots of carbon buildup they struggled to get it all off. and hinted they didn't get it all off.
ah they said premium shell gas at least two tank fills, and then periodically after, it has cleaners in it. and again every once in awhile drive the crap out of it take it to red line,
my daughter's car they were telling her this, stupid traffic these days and cars are fast now to, where the hell are you going to drive it to redline. freeways and hi ways are a traffic jam and your supposed to take it to redline. or she is a young driver, there is a couple of hills big long hills, i will see what we can do stop at the bottom and let it unwind.
stupid since vehicle only has about 11 or 12 thousand miles on it.

oh i mentioned an Italian tune up to the mechanic explaining it to us and he howled with laughter so thanks for that comment.

i hate the stop start so thanks for that.

 

[mike1957]

my car same problem 12 thousand miles bring it in monday what a pain,
the dealer was excellent though they gave us a brand new 2025 forester loaner

 

[Dick Foster]

Autostop Eliminator - Disable The Auto Start Stop Feature

The Autostop Eliminator is an intelligent tech device for your car, truck or SUV that will safely disable auto start-stop feature and remember your preference

www.autostopeliminator.com

 

[mike1957]

so dealers report both cars excessive carbon build up. around pretty much everywhere on pistons, they manually cleaned it as best they could no walnut blasting i guess they scrapped every thing down valves etc the old fashion way. not sure why they didn't blast it. both cars were kept a day longer then estimate, sighting the difficulty of getting the carbon out. kept it and did a cold start, and there were no engine misfires.
to my mind they did the minimum amount so the engine would run with out a misfire. and no check engine light.
its noted in my file, what ever that means to them. plus they loaded the gas tank with fuel cleaner. and told me to run to shell and get premium gas at least two or three tank fills.

they seem to want to blame it all on costco gas. which i pretty much exclusively used, which is annoying to me, costco pumps are so lined up they had to ad more nozzles, so how bad can costco gas be when it seems like the whole world uses it.

staff is nice but i think they did a quick fix not really getting to what the hell the problem is. 11 12 thousand miles and this happens.
any how will run pretty much shell preimum and put a bottle of cleaner in the gas tank, every couple of months.

if it happens again im going to push for a new engine. and or maybe dump the dam thing.
i don't think i would buy subby again.
daughter had tranny problem on her previous cross trek, we were like a couple of hundred miles with in the warranty, other wise it would have amount to 3 or four thousand dollars.

nope can't say i would recommend subby to anyone

 

[bmart]

What Brand Of Gas Does Costco Sell And Is It High-Quality? - SlashGear

Costco offers gas to members for a great price, but what brand of gas is it selling? And is it a high-quality product you'd want to put into your car?

www.slashgear.com

This forum and site have some pretty cool info on fuel, oil, filters, etc.

https://bobistheoilguy.com/forums/threads/costco-fuel-is-top-tier-licensed-pleasantly-surprised.303384/

 

[izzyman]

so dealers report both cars excessive carbon build up. around pretty much everywhere on pistons, they manually cleaned it as best they could no walnut blasting i guess they scrapped every thing down valves etc the old fashion way. not sure why they didn't blast it. both cars were kept a day longer then estimate, sighting the difficulty of getting the carbon out. kept it and did a cold start, and there were no engine misfires.
to my mind they did the minimum amount so the engine would run with out a misfire. and no check engine light.
its noted in my file, what ever that means to them. plus they loaded the gas tank with fuel cleaner. and told me to run to shell and get premium gas at least two or three tank fills.

they seem to want to blame it all on costco gas. which i pretty much exclusively used, which is annoying to me, costco pumps are so lined up they had to ad more nozzles, so how bad can costco gas be when it seems like the whole world uses it.

staff is nice but i think they did a quick fix not really getting to what the hell the problem is. 11 12 thousand miles and this happens.
any how will run pretty much shell preimum and put a bottle of cleaner in the gas tank, every couple of months.

if it happens again im going to push for a new engine. and or maybe dump the dam thing.
i don't think i would buy subby again.
daughter had tranny problem on her previous cross trek, we were like a couple of hundred miles with in the warranty, other wise it would have amount to 3 or four thousand dollars.

nope can't say i would recommend subby to anyone

something isn't right

I showed this to a trusted subaru tech and he was stunned, he had never heard of such a problem

 

[izzyman]

Also, from time immemorial, mechanics have always said to fill up with different fuel brands on a regular basis. There may be some issue with the Costco formulation in your area. Or it could be those particular tanks are bad. In my hometown, years ago there was a story of people having engine failures after using gas from a specific chain of stations. After a couple of years of this problem, it was determined that the owner had taught the staff to check the fuel levels of the tanks and told them to use Comet powder to coat the stick. They used a 20 ft long ruler to measure the fuel level and when it got wet the first time you couldn't tell the level of the second tank. They would always do the first tank with a dry stick so they didn't use the powder on that one, but the subsequent tanks got a dose of Comet scouring powder. Suffice to say they settled out of court